Membrane interactions of fibrillar lysozyme: Effect of lipid bilayer composition

Protein polymerization into amyloid fibrils underlies a number of human disorders, including hereditary systemic amyloidosis arising from fibrillization of the mutated lysozyme. Cell membranes represent one of the main targets for the toxic action of amyloid aggregates. In the present study the impact of monomeric and fibrillar lysozyme on the structural state and physicochemical properties of the model lipid membranes composed of phosphatidylcholine and its mixtures with cardiolipin and cholesterol was investigated using the fluorescence spectroscopy technique. Probing the protein-lipid interactions with the fluorescent probes Laurdan and pyrene showed that both forms of lysozyme give rise to the dehydration of lipid bilayer and decrease of its free volume, but the magnitude of these effects was much more pronounced for the fibrillar protein. The membrane modifying propensity of lysozyme was found to be strongly modulated by the composition of lipid bilayer, with the membrane responses being enhanced by cardiolipin and diminished by cholesterol. (C) 2018 Elsevier B.V. All rights reserved.